Guest Sherbertmelon Posted October 16, 2015 Share Posted October 16, 2015 (edited) Hi guys, I have a manual converted J-spec 1993 NA Supra that is seriously grinding my gears now, I cannot enjoy the car anymore because of this constant stalling issue when coming to a stop. Let me explain. This issue was noticeable from when I installed a Mishimoto radiator and new crank pulley, when I approach a junction, roundabout or come to some kind of stop, as soon as the car goes into neutral the revs 9/10 will just drop and the car will not recover causing it to stall, EVERYTIME the car will fire up instantly again, then the same thing will happen further down the road. I am now forced to try and keep the car rolling at very slow speeds when approaching hoping not to stop but it's really starting to annoy me as that's all i think about. Things I've done and had checked: - New HKS intake was installed to replace cracked air box - TB and Inlet cleaned out - ICV checked and seems to work fine - Supra Specialist adjusted my TPS - No misfiring present - New Radiator and coolant (red) - New Battery (Alternator also seems fine) - Vaccum Lines all fine Note: It also has custom DO Luck dials and the speedo is converted, but I dont see how this would affect anything? Can anybody help? There is posts all over the web will no outcome of what fixed it, and this really doesnt help as know one can work it out :/ I really do not wanna force myself to sell this car, but it's starting to get that way Edited October 16, 2015 by Sherbertmelon (see edit history) Quote Link to comment Share on other sites More sharing options...
Timlowthian Posted October 16, 2015 Share Posted October 16, 2015 I actually have the same issue after converting my NA to TT i was hoping for an easy fix. Mine it only happens when the car is up to temperature, is this the same for yours? I will start by cleaning the idle control valve and throttle body and see how it goes. Quote Link to comment Share on other sites More sharing options...
Scooter Posted October 16, 2015 Share Posted October 16, 2015 Just trying to get more info which may help others diagnose something, but what does it do if you just start it from cold. After a little while it'll start idling a few hundred rpm less every 20-30secs or so, with yours does it keep dropping and stall as it warms up? Quote Link to comment Share on other sites More sharing options...
Jellybean Posted October 16, 2015 Share Posted October 16, 2015 I would check for any Fault codes on the ECU Quote Link to comment Share on other sites More sharing options...
Guest Sherbertmelon Posted October 17, 2015 Share Posted October 17, 2015 I actually have the same issue after converting my NA to TT i was hoping for an easy fix. Mine it only happens when the car is up to temperature, is this the same for yours? I will start by cleaning the idle control valve and throttle body and see how it goes. When my car is cold and the revs are up its fine, only when the car is up to temperature does it suffer. I have cleaned both already - - - Updated - - - I would check for any Fault codes on the ECU I did bridge the two ports in the diagnostics port in engine bay and ECU light just flashed constantly :/ Indicating no logged faults Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted October 17, 2015 Share Posted October 17, 2015 When I have these issues on a car with an idle control valve I put my oscilloscope on 4 of the inputs to the ICV and check that the ecu is sending control signals to it. If it is, I then remove the ICV and send control signals to it on the bench and check it moves quickly and smoothly. At the same time I clean it. If all seems good and it still stalls when refitted I look for air leaks, using a hose to listen with, or a Propane wand to add gas and listen for idle change. Usual causes of an idle speed problem on an N/A MKIV (and many other engines) are a sticking ICV, incorrectly set throttle butterfly stops (people *WILL* fiddle with these without understanding they are factory set, and what the implications are if you disturb them. Those who feel the need to polish things are the worst culprits...), or a leaking PCV valve. Then there are the engines with stellar miles on them where the throttle body is plain worn out. Next come worn or maladjusted throttle position sensors.Get a copy of the engine manual and read the relevant sections if you feel brave and want to do some DIY. Quote Link to comment Share on other sites More sharing options...
Guest Sherbertmelon Posted October 17, 2015 Share Posted October 17, 2015 Just trying to get more info which may help others diagnose something, but what does it do if you just start it from cold. After a little while it'll start idling a few hundred rpm less every 20-30secs or so, with yours does it keep dropping and stall as it warms up? Has never done it from cold as the revs are too high for it to drop out and stall, only when its at full operating temperature. Sometimes the revs will drop so low the car will just about recover but keep it so low the car is vibrating like crazy, most of the time it cannot catch it and just die, it only does this if 1. the car is completely stopped or 2. i put it in neutral but never if the car is in gear and moving even if it is a few mph. If the car can catch the revs and idle whilst stopping it'll be fine until I come to the next stop where by everytime I have no idea what it might actually do. Quote Link to comment Share on other sites More sharing options...
Guest Sherbertmelon Posted October 17, 2015 Share Posted October 17, 2015 ALSO - The car is so random, some days it'll be absolutely fine, no idle drop or stalling at all, other days, like yesterday, stalled 5 times in 20 minutes of driving. Drove me up the wall enough I stopped and went for a walk it was pissing me off that much! Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted October 17, 2015 Share Posted October 17, 2015 Check the resistance of the ECU water temp sender, and it's connector VERY carefully. test resistance hot and cold and compare with the table in the tech section stickies courtesy of Andy Blyth. Quote Link to comment Share on other sites More sharing options...
Guest Sherbertmelon Posted October 17, 2015 Share Posted October 17, 2015 Check the resistance of the ECU water temp sender, and it's connector VERY carefully. test resistance hot and cold and compare with the table in the tech section stickies courtesy of Andy Blyth. Is it highly possible that a bad coolant temp sensor can cause my car to die...driving tonight was fine all the way to tesco, as I floored it back it home got the junction and dead :/ Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted October 17, 2015 Share Posted October 17, 2015 It's possible, so check it. Quote Link to comment Share on other sites More sharing options...
Timlowthian Posted October 18, 2015 Share Posted October 18, 2015 Just had a look at mine and cleaned out the icv and it made no difference. Looked at the ecu water temp sensor and it seems in an awkward place to get the probes on without taking it out so may wait and just order a new one. I have looked into the throttle body as well and I think it looks like someone has played with the throttle stop before I got the engine as appears to be tipex on the thread. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted October 18, 2015 Share Posted October 18, 2015 Hmm, not good, I would start by measuring ecu water temp resistance at the disconnected ECU connector, than, if that doesn't show an issue, I would read the relevant parts of the shop manual and check the throttle pot settings. Quote Link to comment Share on other sites More sharing options...
Guest Sherbertmelon Posted October 19, 2015 Share Posted October 19, 2015 (edited) Hmm, not good, I would start by measuring ecu water temp resistance at the disconnected ECU connector, than, if that doesn't show an issue, I would read the relevant parts of the shop manual and check the throttle pot settings. He has a point, the ECU water temp sensor is in an extremely awkward place, do you know what pin on the ECU plug connects to it? Or no of any diagrams I can view to figure it out? Edit: I found the diagram for the ECU outs, so should I do two tests, one on cold, then plug back in and take out and test on operating temp? Edited October 19, 2015 by Sherbertmelon (see edit history) Quote Link to comment Share on other sites More sharing options...
Guest Sherbertmelon Posted October 21, 2015 Share Posted October 21, 2015 Okay, So I've now tested my water temp sensor and can confirm it's working as it should, my ICV is also confirmed working. I really am lost now, I don't see what it can be. No vac leaks, car starts and runs fine. Just 2-3 times a day it will randomly stall once I've come to a stop or car goes into neutral. Is there anyone out there that could potentially have the answer...if not I'm tempted to sell up (with its known issues) can't keep going on with this recurring issue with no difinitive answer Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted October 22, 2015 Share Posted October 22, 2015 It needs proper diagnostics on it, but I would suspect a throttle pot / or ICV issue myself. How did you confirm the ICV was working? If it were here I'd have a dual channel scope on it, with logging running and drive it until it played up, then look at the log. Quote Link to comment Share on other sites More sharing options...
Scooter Posted October 22, 2015 Share Posted October 22, 2015 You should be able to pick up a ali Y section for an NA complete with all sensors and ready to straight swap for £50 or less. Chris would undoubtably get to the bottom of it but doubt you want to travel, it could be a waste of time and money but seems worth a try given your desperation and the relative lack of cost (you can always sell one on if it doesn't rectify the issue). Quote Link to comment Share on other sites More sharing options...
Timlowthian Posted October 22, 2015 Share Posted October 22, 2015 You should be able to pick up a ali Y section for an NA complete with all sensors and ready to straight swap for £50 or less. Chris would undoubtably get to the bottom of it but doubt you want to travel, it could be a waste of time and money but seems worth a try given your desperation and the relative lack of cost (you can always sell one on if it doesn't rectify the issue). I haven't had a chance to look at anything else on mine due to work since cleaning the ICV. Its interesting that the other member having the same problem is an NA as mine is TT. I have actually done like you mention above and purchased a known working throttle body and inlet with sensors so ill swap that out on my week off next week and rule that out. I also have a new coolant temp sensor as it was only £7 and I want to do a coolant change also so seemed silly not too. Will get readings from it while I am at it. Quote Link to comment Share on other sites More sharing options...
herbiemercman Posted October 22, 2015 Share Posted October 22, 2015 I lived with this exact same problem on my NA, i owned the car from new and it had 42,000 miles on the clock, i had the speed delimiter kph/mph unit fitted when i bought the car. In the past couple of months, prior to me taking the NA/T conversion, the speedo stopped working, at first it was intermitant, but soon became a permanent problem. Then the engine cut outs started, some times the rpm just dropped from the 700 rpm to 400 rpm, only just holding the tick over before stalling, and other times a complete stall, little braking power and no power steering. So i stripped down and cleaned the ICV, (idler control valve), and for a few days it seemed ok, the stalling was intermitant so at that stage i could not know i had cured the problem. I found out that the delimiters / kph / mph converters were known to cause this very problem. When my car went for it's NA/T conversion my NA/T man replaced the delimiter unit and the problem was solved. Hope this helps. herbiemercman. Quote Link to comment Share on other sites More sharing options...
evinX Posted October 22, 2015 Share Posted October 22, 2015 Mine used to try and cut out at slow speed. Had a knackered throttle body on a auto, pull yours off, put it against light and see if any comes through in the closed position, none should come through. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted October 22, 2015 Share Posted October 22, 2015 It should, actually, the TB is set to have a slightly open setting on "closed" throttle. Quote Link to comment Share on other sites More sharing options...
evinX Posted October 23, 2015 Share Posted October 23, 2015 It should, actually, the TB is set to have a slightly open setting on "closed" throttle. Mine didn't like it, got me a throttle body that lets only a pixel of like through near the shaft and sorted it, had 2 throttle bodys with light through it and my supra hunted and idled very high, tried different icv's...tps...same thing. Quote Link to comment Share on other sites More sharing options...
Timlowthian Posted October 28, 2015 Share Posted October 28, 2015 Ok so in my week off I have been looking into this and had some good and bad news. I started by swapping over a different throttle body with all sensors and a different ecu. It helped and the car didnt stall at all anymore but it did not want to rev properly. I then left it for the day and went back to it but now it starts but immediately dies and throws an engine code error. I have refitted the old ecu and throttle body and it still gets the same. The error code is 31 which I believe is the map sensor. On research online people mention the fcd and speedo converters to blame but I havent fitted these yet. Any help on what to try would be much appreciated. Quote Link to comment Share on other sites More sharing options...
Fitz Posted August 4, 2016 Share Posted August 4, 2016 Seems like my car has started down this route again. Coming to a stop or sitting in traffic the revs sometimes drop down and will either A) Catch itself and maintain idle or B) Cut out - Car is an NA-TT Auto. I had this problem about 9 months ago but was rectified as it was a 'broken wire in the engine loom' that was fixed - however after having some minor work done on the car the problem has started up again. The car has a HKS FCD fitted that I purchased brand new and has never given me any problems that I know of and it has UK clocks as AFAIK, there is no speedo convertor in there. Bit concerned as I only really use the car when I'm collecting/dropping of the kids so don't want anything bad to happen if they're in the car with me. Quote Link to comment Share on other sites More sharing options...
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